This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. In both selenium and vitamin E, the strongest evidence for their potential roles in preventing prostate cancer comes from secondary findings of two randomized, placebo-controlled clinical trials. The development of these two supplements has arrived at the stage where a randomized, placebo-controlled intervention is needed to test the primary hypothesis regarding these supplements'prostate cancer chemoprevention effects. Data indicate that activities of selenium and vitamin E are complementary and that the two supplements act synergistically to inhibit carcinogenesis. This evidence makes the 2 x 2 factorial design for simultaneously testing both supplements a particularly attractive option for the confirmatory Phase III trial. We hypothesize that Vit E &/or Selenium Supplements would prevent or decrease Prostate Cancer. The aims are to assess the effect of selenium and vitamin E alone and in combination on the clinical incidence of prostate cancer. Study duration will be twelve years, with a five-year uniform accrual period and a minimum of seven years of treatment. Participants will receive study medication until a common point in time (the entire length of the trial is between seven and twelve years depending on when the participant was randomized. The study will help evaluate the therapeutic efficacy of this intervention on prostate cancer I